Drillable bridge plug

Abstract

A method and apparatus for use in a subterranean well is described. The apparatus typically includes a mandrel and a packing element. The mandrel may have an outer surface and a non-circular cross-section and a the packing element may be arranged about the mandrel, the packing element having a non-circular inner surface matching the mandrel outer surface such that concentric rotation between the mandrel and the packing element is precluded. The apparatus may include slips having cavities to facilitate removal of the apparatus. The apparatus also may include a valve for controlling fluid flow through a hollow mandrel. The valve may include a flapper having at least one tab to engage at least one recession in the mandrel such that rotation between the mandrel and the valve is precluded when the valve is in a closed position. The apparatus may further include a central member which is releaseably attached to the mandrel by a release mechanism.

1. A subterranean apparatus comprising:
 a hollow mandrel having an inner diameter defining a passage therethrough; 
 a packing element arranged about the mandrel; and 
 a valve functionally associated with the mandrel for selectively controlling flow of fluids through the passage, the valve having a flapper with a non-circular cross section adapted to selectively engage the mandrel such that rotation between the mandrel and the valve is precluded when the valve is in a closed position. 
 
   
   
     2. The apparatus of  claim 1  wherein the flapper having the non-circular cross section is adapted to selectively engage the inner diameter of the mandrel, the inner diameter of the mandrel being non-circular, when the valve is in the closed position. 
   
   
     3. The apparatus of  claim 1  in which
 the valve has at least one tab adapted to selectively engage at least one recession in the mandrel when the valve is in the closed position. 
 
   
   
     4. The apparatus of  claim 3  in which the valve has a hinge to pivotally attach the flapper to the mandrel. 
   
   
     5. The apparatus of  claim 3  wherein the flapper is biased in the closed position by a spring. 
   
   
     6. The apparatus of  claims 1  or  3  wherein the valve further comprises a seal to sealingly engage the flapper and the mandrel when the valve is in the closed position. 
   
   
     7. The apparatus of  claim 6  wherein the seal comprises a bonded seal on the flapper. 
   
   
     8. The apparatus of  claim 6  wherein the seal comprises an O-ring on the mandrel. 
   
   
     9. The apparatus of  claim 6  wherein the seal comprises an elastomeric sealing element functionally associated with the mandrel. 
   
   
     10. The apparatus of  claim 2  or  3  wherein the flapper is comprised of non-metallic material. 
   
   
     11. The apparatus of  claim 3  or  10  wherein the non-metallic material is fiber-reinforced thermoset, fiber reinforced thermoplastic, or structural grade plastic. 
   
   
     12. The apparatus of  claim 1  further comprising a central member within the passage of the mandrel, the central member being selectively releasable from the apparatus. 
   
   
     13. The apparatus of  claim 12  wherein the central member is releaseably attached to the mandrel by a release mechanism. 
   
   
     14. The apparatus of  claim 13  wherein the release mechanism is comprised of shear screws. 
   
   
     15. The apparatus of  claim 12  wherein the release mechanism is comprised of shear rings, adjustable spring-loaded detent pins, or rupture disks. 
   
   
     16. The apparatus of  claim 1  wherein the mandrel has an outer surface, the mandrel having a non-circular cross-section, the packing element having a non-circular inner surface such that rotation between the mandrel and the packing element is precluded, the outer surface of the mandrel and the inner surface of the packing element interfering with one another in rotation. 
   
   
     17. The apparatus of  claim 16  wherein the mandrel comprises non-metallic materials. 
   
   
     18. The apparatus of  claim 16  in which the mandrel is comprised of a metallic core wound with thermoplastic tape. 
   
   
     19. The apparatus of  claim 18  wherein the metallic core is comprised of brass and the tape is reinforced with carbon fiber. 
   
   
     20. The apparatus of  claim 16  further comprising an anchoring assembly arranged about the mandrel, the anchoring assembly having a non-circular inner surface such that rotation between the mandrel and the anchoring assembly is precluded. 
   
   
     21. The apparatus of  claim 20  wherein the anchoring assembly further comprises:
 a first plurality of slips arranged about the non-circular mandrel outer surface, the slips being configured in a non-circular first loop such that rotation between the mandrel and the first plurality of slips is precluded by interference between the first loop and the mandrel outer surface; 
 a first slip ring surrounding the first plurality of slips to detachably hold the first plurality of slips about the mandrel; 
 a second plurality of slips arranged about the non-circular mandrel outer surface, the second plurality of slips being configured in a second non-circular loop such that concentric rotation between the mandrel and the second loop is precluded by interference between the second loop and the mandrel outer surface; and 
 a second slip ring surrounding the second plurality of slips to detachably hold the second plurality of slips about the mandrel. 
 
   
   
     22. The apparatus of  claim 21  wherein each the first plurality of slips and second plurality of slips each contain a cavity. 
   
   
     23. The apparatus of  claim 22  further comprising:
 a first cone arranged about the non-circular outer surface of the mandrel, the first cone comprising a non-circular inner surface such that rotation between the mandrel and first cone is precluded, wherein a second plurality of slips abuts the first cone, facilitating radial outward movement of the slips into engagement with the wellbore wall upon traversal of the first plurality of slips along the first cone; 
 a second cone arranged about the non-circular outer surface of the mandrel, the second cone comprising a non-circular inner surface such that rotation between the mandrel and second cone is precluded, wherein a second plurality of slips abuts the second cone, facilitating radial outward movement of the slips into engagement with the wellbore wall upon traversal of the second plurality of slips along the second cone, the first and second cones each comprising a plurality of channels, each of the plurality of channels being receptive of at least one of the plurality of slips, the channels being arranged such that rotation between the first cone and the first slips is precluded, and the second cone and the second slips is precluded. 
 
   
   
     24. The apparatus of  claim 16  wherein the packing element further comprises a first end element, a second end element, and an elastomer disposed therebetween. 
   
   
     25. A method of selectively isolating a portion of a well comprising the steps of:
 providing an apparatus having a hollow mandrel with an inner diameter defining a passage therethrough, the inner diameter of the mandrel having a non-circular cross section, a packing element arranged about the mandrel, and
 a valve functionally associated with the mandrel for selectively controlling flow of fluids through the passage, the valve having a flapper with a non-circular cross section, adapted to engage the inner diameter of the mandrel such that rotation between the mandrel and the valve is precluded when the valve is in a closed position; 
 
 running an apparatus into a well, 
 setting the packing element by the application of a force; 
 selectively controlling a flow of fluid through the apparatus by the valve; and 
 destructively removing the apparatus including the valve out of the well. 
 
   
   
     26. The method of  claim 25  in which the step of providing an apparatus further comprises providing the apparatus with a flapper having at least one tab, the mandrel having at least one recession, and further comprising:
 closing the valve, the at least one tab engaging the at least one recession when the valve is closed. 
 
   
   
     27. The method of  claim 26  further comprising:
 sealing the valve against the mandrel when the valve is closed with a seal. 
 
   
   
     28. A method of selectively isolating a portion of a well comprising the steps of:
 providing an apparatus having a hollow mandrel with an inner diameter defining a passage therethrough, a packing element arranged about the mandrel, and a valve functionally associated with the mandrel for selectively controlling flow of fluids through the passage, the valve having a flapper having a non-circular cross section, adapted to engage the inner diameter of the mandrel such that rotation between the mandrel and the valve is precluded when the valve is in a closed position; 
 running an apparatus into a well, 
 setting the packing element by the application of a force; 
 selectively controlling a flow of fluid through the apparatus by the valve; and 
 destructively removing the apparatus including the valve out of the well, by 
 milling the apparatus out of the well, the flapper of the apparatus being comprised of non-metallic material to facilitate the milling. 
 
   
   
     29. The method of  claim 26  in which the step of providing an apparatus further comprises providing the apparatus with a central member, the method further comprising:
 preventing fluid flow through the apparatus by the central member. 
 
   
   
     30. The method of  claim 29  further comprising:
 selectively releasing the central member from the passage of the apparatus; and 
 controlling fluid flow through the apparatus with the valve. 
 
   
   
     31. The method of  claim 30  further comprising:
 selectively operating a release mechanism to selectively release the central member. 
 
   
   
     32. The method of  claim 31  in which the step of providing an apparatus includes providing the apparatus with the mandrel having an outer surface and a non-circular cross-section, the packing element having a non-circular inner surface such that rotation between the mandrel and the packing element is precluded, the outer surface of the mandrel and inner surface of the packing element interfering with one another in rotation. 
   
   
     33. The method of  claim 32  further comprising:
 locking an anchoring assembly of the apparatus to the mandrel to lock the apparatus in place within the well. 
 
   
   
     34. A subterranean apparatus comprising:
 a hollow mandrel having an inner diameter defining a passage therethrough; 
 a packing means arranged about the mandrel; and 
 a valve functionally associated with the mandrel for selectively controlling flow of fluids through the passage, the valve having means for engaging the mandrel such that rotation between the mandrel and the valve is precluded when the valve is in a closed position to facilitate subsequent removal of the apparatus, the means for engaging the mandrel being a flapper with a non-circular cross section adapted to selectively engage the mandrel, the apparatus having a central member within the passage of the mandrel, the central member having selective releasing means. 
 
   
   
     35. The apparatus of  claim 34  further comprising means for anchoring the apparatus in a wellbore.